Note 12 - Revenue by Product Group, by Significant Customer and by Geographic Location; Geographic Information - Total Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 29,772	$ 29,697	$ 30,418	$ 24,723	$ 26,956	$ 26,787	$ 30,548	$ 21,264	$ 114,610	$ 105,555	$ 113,420
Percentage of Revenue									100.00%	100.00%	100.00%
UNITED STATES
Revenue									$ 90,302	$ 85,351	$ 92,905
Percentage of Revenue									79.00%	81.00%	82.00%
Europe [Member]
Revenue									$ 14,744	$ 11,730	$ 12,435
Percentage of Revenue									13.00%	11.00%	11.00%
Other Location [Member]
Revenue									$ 9,564	$ 8,474	$ 8,080
Percentage of Revenue									8.00%	8.00%	7.00%